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31.
Alok Chakrabarty Pradipta Purkayastha Nitin Chattopadhyay 《Journal of photochemistry and photobiology. A, Chemistry》2008,198(2-3):256-261
The cis-skew to trans-planar photoisomerization of benzil in the photoexcited state was studied by laser-induced optoacoustic spectroscopy (LIOAS) in a series of normal alkane solvents at room temperature. The structural volume change due to the photoisomerization process has been estimated and compared with the same calculated from the optimized skew and trans structures. The magnitude of the structural volume change is estimated to be 22.9 ± 1.2 mL/mol. This study reveals that an expansion in volume occurs during the photoinduced isomerization process. In non-polar alkane solvents, the estimated volume change has been argued to be free from electrostrictional contribution. 相似文献
32.
Kabita Chakrabarty Prabirkumar Saha Aloke Kumar Ghoshal 《Journal of membrane science》2010,346(1):37-44
This paper presents an experimental investigation on facilitated and simultaneous transport of mercury and lignosulfonate (LS) through a flat sheet supported liquid membrane (SLM) having Nylon 6,6 as support, trioctylamine (TOA) as carrier and dichloroethane as solvent. The experiments were performed at various operating conditions such as strip phase concentration, feed pH, carrier concentration and feed concentration to find the best set of parameters that would yield the maximum separation of pure mercury as well as its mixture with LS. The experiments were performed in co-transport mode using NaOH as the strip phase. It was observed that extraction of mercury as well as its mixture increases with increase in concentration of NaOH up to a certain limit 0.1 M NaOH in case of pure solution and 0.2 M NaOH in case of mixture). Feed phase pH significantly affects the mercury separation process. However, initial feed concentration does not affect the extraction process appreciably. Separation of mixture of mercury and LS behaves in a similar way as their pure solution; however the extraction is low in comparison to pure solution. The extraction of mercury from its pure solution is about 81% in 1 h. The extraction of mercury and LS from their mixture is about 52.6% and 50.2%, respectively at optimum condition and in a period of 2 h. 相似文献
33.
34.
Ronhovde P Chakrabarty S Hu D Sahu M Sahu KK Kelton KF Mauro NA Nussinov Z 《The European physical journal. E, Soft matter》2011,34(9):105
We elaborate on a general method that we recently introduced for characterizing the “natural” structures in complex physical
systems via multi-scale network analysis. The method is based on “community detection” wherein interacting particles are partitioned into an “ideal
gas” of optimally decoupled groups of particles. Specifically, we construct a set of network representations (“replicas”)
of the physical system based on interatomic potentials and apply a multiscale clustering (“multiresolution community detection”)
analysis using information-based correlations among the replicas. Replicas may i) be different representations of an identical
static system, ii) embody dynamics by considering replicas to be time separated snapshots of the system (with a tunable time
separation), or iii) encode general correlations when different replicas correspond to different representations of the entire
history of the system as it evolves in space-time. Inputs for our method are the inter-particle potentials or experimentally
measured two (or higher order) particle correlations. We apply our method to computer simulations of a binary Kob-Andersen
Lennard-Jones system in a mixture ratio of A80B20 , a ternary model system with components “A”, “B”, and “C” in ratios of A88B7C5 (as in Al88Y7Fe5 , and to atomic coordinates in a Zr80Pt20 system as gleaned by reverse Monte Carlo analysis of experimentally determined structure factors. We identify the dominant
structures (disjoint or overlapping) and general length scales by analyzing extrema of the information theory measures. We
speculate on possible links between i) physical transitions or crossovers and ii) changes in structures found by this method
as well as phase transitions associated with the computational complexity of the community detection problem. We also briefly
consider continuum approaches and discuss rigidity and the shear penetration depth in amorphous systems; this latter length
scale increases as the system becomes progressively rigid. 相似文献
35.
This paper presents a method for the evaluation of the capacitance of the dielectric coated metallic plates forming a corner using the method of moments based on the pulse basis function and the point matching. Two integral equations are formed based on the boundary conditions for the potential on the conductor surface and continuity of the normal component of the displacement flux density at the dielectric-free space interface. A set of simultaneous equations are formed from the two integral equations using the method of moments. The total free charge on the conductor surface is found from the solution of the set of simultaneous equations. Numerical data on the capacitance and the charge distribution are presented. The validity of the analysis has been justified by comparing the data on the capacitance that is available in the literature for a metallic structure with the data on the capacitance computed with the present method for a similar structure considering a very low dielectric constant as well as a very thin dielectric coating. Further validation has been carried out by comparing the capacitance data of the specific case when the angle between two metallic plates is 180° forming a dielectric coated metallic rectangular plate for which the capacitance data are available in the literature. 相似文献
36.
S. M. Islam Sanchita Mondal Anupam Singha Roy Paramita Mondal Manir Mobarak Dildar Hossain Palash Pandit 《Transition Metal Chemistry》2010,35(3):305-313
A polymer-anchored Pd(II) Schiff base complex has been synthesized by reacting a polymeric amine with 2-pyridinecarboxaldehyde
to get the polymer-anchored Schiff base, which was then reacted with palladium acetate. The catalyst was characterized by
physicochemical and spectroscopic methods. It shows excellent catalytic activity in the Sonogashira coupling of phenylacetylene
with aryl halides using triethylamine as a base and copper iodide as a co-catalyst in water under open air at 70 °C. We have
also studied the effects of base and solvent on the coupling reaction. Sonogashira reactions of phenylacetylene with a variety
of functionalized aryl halides were performed under the optimized reaction conditions. This catalyst gives excellent yields
without the use of phosphine ligands. Further experiments showed that the catalyst can be used five times without much loss
in the catalytic activity. 相似文献
37.
The p53 protein activation protects the organism from propagation of cells with damaged DNA having oncogenic mutations. In normal cells, activity of p53 is controlled by interaction with MDM2. The well understood p53-MDM2 interaction facilitates design of ligands that could potentially disrupt or prevent the complexation owing to its emergence as an important objective for cancer therapy. However, thermodynamic quantification of the p53-peptide induced structural changes of the MDM2-protein remains an area to be explored. This study attempts to understand the conformational free energy and entropy costs due to this complex formation from the histograms of dihedral angles generated from molecular dynamics simulations. Residue-specific quantification illustrates that, hydrophobic residues of the protein contribute maximum to the conformational thermodynamic changes. Thermodynamic quantification of structural changes of the protein unfold the fact that, p53 binding provides a source of inter-element cooperativity among the protein secondary structural elements, where the highest affected structural elements (α2 and α4) found at the binding site of the protein affects faraway structural elements (β1 and Loop1) of the protein. The communication perhaps involves water mediated hydrogen bonded network formation. Further, we infer that in inhibitory F19A mutation of P53, though Phe19 is important in the recognition process, it has less prominent contribution in the stability of the complex. Collectively, this study provides vivid microscopic understanding of the interaction within the protein complex along with exploring mutation sites, which will contribute further to engineer the protein function and binding affinity. 相似文献
38.
Sanchita Mondal Saikat Kumar Manna Kalipada Maiti Rajkishor Maji Syed Samim Ali Srimanta Manna 《Supramolecular chemistry》2017,29(8):616-626
A FRET-based chemosensor L containing donor phenanthroline and acceptor fluorescein moiety was designed, synthesised and characterised for the ratiometric fluorescent detection of Cu2+ in organo-aqueous solution. Probe L showed high selectivity and excellent sensitivity towards Cu2+ ions by exhibiting both colorimetric and fluorometric changes due to opening of the spirolactum ring of fluorescein upon complexation with Cu2+. In presence of Cu2+ ions, probe L formed L-Cu2+ complex in 1:1 stoichiometric fashion which is established on the basis of Job’s plot and mass spectroscopy. We also performed DFT computational studies to know the binding nature and coordination feature of the complex. Furthermore, fluorescence imaging studies revealed that probe L was cell permeable and could be used to detect intracellular Cu2+ in living cells. 相似文献
39.
Manirul?IslamEmail author Dildar?Hossain Paramita?Mondal Kazi?Tuhina Anupam?Singha?Roy Sanchita?Mondal Manir?Mobarak 《Transition Metal Chemistry》2011,36(2):223-230
A thiosemicarbazone Cu(II) complex anchored to a polystyrene framework has been synthesized and characterized by analytical
and spectroscopic techniques. The complex was found to be a highly active catalyst for the oxidation of various organic substrates
including alkenes and alcohols using H2O2 as oxidant. The reaction conditions were optimized with respect to temperature, solvent, oxidant, catalyst amount, and substrate
to peroxide ratio. The heterogeneous catalyst was reused five times without significant loss of activity. A comparison between
the catalytic activities of this polymer-supported Cu(II) complex and its homogeneous analogue was carried out. 相似文献
40.
Deeparnab Chakrabarty Nikhil R. Devanur Vijay V. Vazirani 《Mathematical Programming》2011,130(1):1-32
Determining the integrality gap of the bidirected cut relaxation for the metric Steiner tree problem, and exploiting it algorithmically, is a long-standing open problem. We use geometry to define an LP whose dual is equivalent to this relaxation. This opens up the possibility of using the primal-dual schema in a geometric setting for designing an algorithm for this problem. Using this approach, we obtain a 4/3 factor algorithm and integrality gap bound for the case of quasi-bipartite graphs; the previous best integrality gap upper bound being 3/2 (Rajagopalan and Vazirani in On the bidirected cut relaxation for the metric Steiner tree problem, 1999). We also obtain a factor \({\sqrt{2}}\) strongly polynomial algorithm for this class of graphs. A key difficulty experienced by researchers in working with the bidirected cut relaxation was that any reasonable dual growth procedure produces extremely unwieldy dual solutions. A new algorithmic idea helps finesse this difficulty—that of reducing the cost of certain edges and constructing the dual in this altered instance—and this idea can be extracted into a new technique for running the primal-dual schema in the setting of approximation algorithms. 相似文献